Séminaire spécialisé

lundi 4 juin 2012 à 12:00

Amphi G. Besse

Rotavirus: Deposition, Aggregation and Inactivation Kinetics

Helen Nguyen

University of Illinois at Urbana-Champaign

Rotavirus is the most common enteric virus that causes severe diarrhea, vomiting and acute dehydration among children. Approximately 600,000 children die worldwide every year because of intestinal complications due to rotavirus infection. We are using an interdisciplinary approach to identify chemical and physical factors that influence attachment, mobility, and inactivation of rotavirus and bacteriophage MS2, a common surrogate for enteric virus. Our specific objectives include: (1) to determine aggregation rates of rotavirus and MS2 in solution with systematically modified composition; (2) to determine the attachment rates of rotaviruses and MS2 on inorganic (i.e. quartz) and organic (i.e. coated with natural organic matter) soil surfaces at the microscopic scale; (3) to determine the inactivation kinetics of rotavirus and MS2 irradiated with sun-light.

Aggregation kinetics of rotavirus in aqueous solutions and its deposition kinetics on silica surface were studied using complementary techniques of time-resolved dynamic light scattering (TR-DLS) and quartz crystal microbalance (QCM). Experimental results for both rotavirus and MS2 suggest that besides electrostatic interactions, steric repulsions and specific interaction with divalent cations are important mechanisms in controlling the deposition and aggregation kinetics of rotavirus and MS2.

Indirect (UVA-visible spectrum) damage by exogenous sensitizers, indirect (UVB and UVA) damage by endogenous sensitizers, and direct UVB damage have been identified as three sunlight inactivation mechanisms for pathogens. Below 25°C, the indirect exogenous and endogenous damage were experimentally similar for rotavirus. Above 50°C, rotavirus inactivation was primarily due to heat damage. Quencher tests indicated that singlet oxygen and hydrogen peroxide were not explicitly responsible for rotavirus inactivation from ~32 to 50°C. While indirect UVA exogenous damage was significant for MS2 over 14-40°C, this mechanism should be considered for rotavirus over a higher range of temperature from 32 to 50°C. The observed difference in inactivation of MS2 and of rotavirus suggested that it is crucial to investigate disinfection using enteric viruses.